I've looked in both the forum and on the Piriform Defraggler Docs Documentation site to get an idea of things such as frequency of defragging to assure best system performance and can't find anything regarding professional opinion regarding the matter. I realize this matter is very subjective by its nature, however figure since Piriform builds it, they also ought to have some thoughts on the matter. Is there anywhere I can find such a thing?
Any info you find will be the opinion of the author.
And as you say, it will be completely subjective.
No one answer will apply to the wider audience.